Switching means for interconnecting coaxial conductors



March 21, 1944. w .KRAM ETAL SWITCHING MEANS FOR INTERCONNECTING CO'-AXIAL GONDUCTORS 2 Sheets-Sheet 1 Filed May 16, 1942 ATTORNEY March 21, 1944. w, KRAM AL 2,344,780

SWITCHING MEANS FOR INTERCONNECTING CO-AXIAL CONDUCTORS Filed May 16, 1942 2 Sheets-Sheet 2 Fig. 3.

INVENTORS Patented Mar. 21, 1944 SWITCHING MEANS FOR- INTERCONNECT- ING GOAXIAL CONDUCTORS Walter Exam and Frank Lewis John Jarvis, London, England, assignors to International Standard Electric Corporation, New York, N. Y.

Application May 16, 1942, Serial No. 443,286 In Great Britain June 11, 1941 8 Claims. (Cl. 118-44) This invention relates to the switching of coaxial conductors, e. g. coaxial cords or coaxial cables, and is an improvement in or modification of the invention for which United Kingdom Patent No. 513,287 was granted. For convenience hereinafter the term cable is used generically, the term conductor being reserved for the inner and outer elements of the cable.

Due to the higher frequencies employed in telecommunication the use of coaxial cables has become more frequent in apparatus-notably in testing gear.

One of the problems met with in the use of coaxial cables is the difficulty of quickly switching from one ,cable to another and still maintaining complete individual screening of the inner conductors. This complete screening oi the inner conductors is essential in most circuits owing to the possibility of crosstalk occurring due to the high difference in level in the cables being switched. Another requirement is that as little impedance mismatching as possible be presented to the cables. It is also essential that contact resistance be low, especially the screen contacts, so that a low earth impedance can be maintained,

Advantages oi the present invention are: the avoidance of extensions of the inner conductors, in other words the complete screening of the inner conductors; a, rigorous wiping action, so that the contacts are maintained in a clean condition; and ready adaptability for switching of one incoming line to a number of outgoing lines. For

a specific use to which the invention has been put, namely as a change-over switch of a filter test set, the further advantage is oflered that it becomes possible to incorporate the appropriate terminating resistance in a fully screened condition.

The invention consists in a device for connecting together two of a plurality of coaxial cables while maintaining complete screening 01 the inner conductors from each other and externally.

A typical case in which a switch in accordance with the present invention has been found useful is in a certain H. F. filter test set where the switch in the measure-test position had to be'capable of switching a coaxial cable to either of two other coaxia1 cables at will, the unconnected cable being terminated with a 750 resistance. The cables being switched might at any time have a diilference in level of anything up to 80 db., while it was essential to switch the screens of the cables together with the inner conductors.

An embodiment of the invention as used in that case has been shown in the accompanying drawings and will now be described, the three figures oi the drawings being sections on the respective lines i-l, 2-2, 2-3.

In the drawings, a mounting plate I of insulating material carries four Phosphor-bronze studs 2 and 3 and a Phosphor-bronze bearing piece 4. The studs 2 carry inner nickel silver studs ii insulated from them by the pieces 6. The inner conductors of the two outgoing coaxial cables, to both of which the incoming cable can be switched, are connected to the studs 5, the screens oi the cables being connected via the sleeves l to the studs 2. The pieces 8 are for clamping the ends of the sleeves "i on to the screens of the cables. The incoming cable is oonnectedin a similar manner to the bearing piece 4 and the central stud 9 carried in and insulated from the piece 4. The studs 3 which are also carried by the mounting plate l are plain flat top studs spring loaded by the springs i0, restriction of movement being eiiected by the two iocknuts.

The rotor plate ii, of insulating material, carries a brass chamiel-shaped block I: which has two tubes turned upon-it, One of these tubes is a running fit in the bearing piece 4; the other tube, by turning the rotor plate about its bearing, makes contact with either or the two studs 2. This tub also carries a nickel silver stud is which is secured into an insulating plug M. This plug is a sliding lit in the tube and is urged toward the stud 5 by the flat Phosphor-bronze spring 15, the other end of which bears on the stud 9. The spring is kept centrally in the channel piece it by the ebonite spacer It. It will be seen that the channel piece i 2 has a brass covering strip ll secured to it.

Thus by rotating the rotor plate ll about the bearing 4 one may make electrical contact between the inner conductor and the screen 01' the incoming cable and the inner conductor and the screen or either of the two outgoing cables. The inner conductors i and s of the two cable terminations on the face of the panel I and the connection between them over members l3 and I5, are completely screened by reason or the cablelike formation of the connecting member H, H etc.

The rotor plate II also has secured to it another brass channel-shaped piece is which again has two tubes turned upon it. The ends of these tubes bear against the studs 2 and 2 on the mounting plate I. Two nickel silver studs I! secured into insulating plugs which are a sliding at in the tubes. are urged by the springs 20 to studs 3 or I (dependent upon position of the rotor plate). Across the inner cndsofthestudsllisconnecteda750resist- The drive is transmitted from the spindle by a pin working in a slot in the bush is; the reason for thisindirect method of coupling the spindle will be evident later. The spindle runs in a bearing II which is supported in the plate is which in turn is secured to the mounting plate I by the four pillars 21. A spring is is iitted to urge the rotor towards the mounting plate I so as to maintain good electrical contact between the sets of contact studs on the rotor plate II and the mounting plate i.

A "click" mechanism is provided to locate the switch correctly in the two positions. This consistsofaballllwhichiscarriedinacagell secured in the mounting plate i and which locates in either of two holes in the plate ll secured to the rotor plate ll. When the ball locates in one of these holes the appropriate contact studs are lined up. Adjustment for the ball is provided by the screw 3!.

It will be noted that in turning the switch from one position to the other, the ball 2! forces the rotor away from the mounting plate I. The spindle is will allow this to happen as the drivtive cables outer terminal sleeves and inner terminal posts" ing pin in the end of the spindle will slide in the slot in the bush II. The advantage of this lifting-o8" is the reduction in friction due to the smaller area then in contact between the studs on the mounting plate i and the rotor.

While the embodiment shown is of a form suited to perform a specialised switching operation the straightforward case of a multiple coaxial stud switch is obvious.

It will be seen that by this design complete screening of the inner conductors of the coaxial cables from each other and externally is maintained at all times; that, due to the slight rubbing of the contact studs before lifting-oi!" occurs, low resistance contacts are maintained, this low resistance contact being most essential in the screen circuit; and that, owing to the comparatively short path between the incoming and outgoing cables no serious impedance mismatching will occur.

What is claimed is:

1. A switch device for connecting two of a plurality of co-asial cables, comprising a supporting member, cable terminal members for the respective cables supported therein and consisting of outer terminal sleeves and inner terminal elements insulated therefrom, a shiftable switch member having connected inner and connected outer contact elements movable therewith to em gage the respective inner and outer cable terand supplemental switching minals of two of the cables for closing of the circuits through the inner and outer terminals thereof and supplemental switching means having contact members and a resistance in a series therewith and adapted to engage respectively with the inner and outer terminal elements of a then non-connected cable.

2. A switch device for connecting two of a plurality of co-axial cables, comprising a supporting member, cable terminal members for the respecsupported therein and consisting of insulated therefrom, a rotary switch member having connected inner and connected outer contact elements movable therewith to engage the respective inner and outer cable terminals of two of the cables for closing the circuits therethrough and supplemental switching means rotatively connected with the rotary switch member and hav-' ing contact members connected to a resistance in series therewith and adapted to engage respectively with the inner and outer terminal elements'of a then non-connected cable and means to eifect yielding pressure engagement between the switch contacts and the cable terminal members.

3. A switch device for connecting two of a plurality of co-axial cables, comprising a supporting member, cable terminal members for the respective cables supported therein and consisting of outer terminal sleeves and inner terminal posts insulated therefrom, a rotatable switch member having connected inner and connected outer contact elements movable therewith to engage the respective inner and outer cable terminals of two of the cables for closing of the circuit through the inner and outer terminals thereof and supplemental switching means rotatively connected with the switch member and having contact members and a resistance in a series therewith and adapted to engage respectively with the inner and outer terminal elements of a then non-connected cable, said rotatable switch member and supplemental switching means being supported to permit retractive movement relative to the terminal members and resilient means operative to urge the switch members into pressure contactengagement with the terminals.

4. A switch device for connecting two of a plurality of Ito-axial cables, comprising a supporting member, cable terminal members for the respective cables supported therein and consisting of outer terminal sleeves and inner terminal posts insulated therefrom, a rotatable switch member having connected inner and connected outer contact elements movable therewith to engage the respective inner and outer cable terminals of two of the cables for closing of the circuit through the inner and outer terminals thereof means rotatably connected with the switch member and having contact members and a resistance in series therewith and adapted to engage respectively with the inner and outer terminal elements of a then nimconnected cable, said rotatable switch member being supported to permit retractive movement relative to the terminal member, resilient means operative to urge the switch members into pressure contact engagement with the terminals and engaging latching means carried by the supporting member and the rotatable switch member adapted yieldably to retain said members in stop position and resiliently to eifect lifting release of the contacts during movement from engaging position.

5. A switch device for connecting two co-axial cables alternatively to a third co-axial cable comprising a supporting member, cable terminal members for the respective cables supported therein and consisting of outer terminal sleeves and inner terminal posts insulated therefrom, the sleeve of one of said terminals being inwardly extended to provide a. bearing portion, a rotatable switch member journaled in said bearing portion and having connected inner and connected outer contact elements movable therewith to engage the respective inner and outer cable terminals, a supplemental switching means carried by the switch member and provided with duplicate concentrically supported contact members and a resistance in series therewith and adapted to engage respectively with the inner and outer terminal elements of the non-connected cable and spring pressed switch studs fitted to the supporting member and positioned for completing the circuit of the supplemental switching means and said rotatable switch member and supplemental switching means being supported to permit retractile movement relative to the terminal member and co-axially supported operating means for the rotatable switch member journaled to permit movement longitudinally of its axis of rotation and having resilient means engaged therewith to urge the switch members into pressure contact engagement with the terminals.

6. A switch device for connecting two of a plurality of co-axial cables comprising a supporting member, cable terminal members for the respective cables supported therein and consisting of outer terminal sleeves and inner terminal elements insulated therefrom. a rotatable switch member having connected inner and connected outer contact elements movable therewith to engage the respective inner and outer cable terminals of two of the cables for closing of the circuits through the inner and outer terminals thereof.

7. A switch device for connecting two of a plurality of co-axial cables comprising a supporting member, cable terminal members for the respective cables supported therein and consisting of outer terminal sleeves and inner terminal elements insulated therefrom, a rotatable switch member having connected inner and connected outer contact elements movable therewith to engage the respective inner and outer cable terminals of two of the cables for closing of the circuits through the inner and outer terminals thereof and said switch member being provided with screening means for protection of the circuits against induction interference.

8. A switch device for connecting two of a plurality of co-axial cables comprising a supporting member, cable terminal members for the respective cables supported therein and consisting of outer terminal sleeves and irmer terminal elements insulated therefrom, a rotatable switch member having connected inner and connected outer contact elements movable therewith to engage the respective inner and outer cable.ele-

' ments of two of the cables for the closing of the circuits thereof and means to efiect yielding pressure engagement between the switch contact elements and the cable terminal elements.

WALTER KRAM. FRANK LEWIS JOHN JARVIS. 

